5 Comet Facts: Dirty Snowballs of the Solar System
Comets are balls of frozen gases mixed with pieces of rocks, water and ice. There are only a hundred or so named comets and a bit over 3500 known comets.
Most comets reside in the outer edge of the solar system in the Oort cloud. When frozen, comets are the size of a small town.
Although not proven, some scientists credit comets the cause of the death of dinosaurs. This is because comets travel at enough speed that could release the energy to create an extinction event.
So, let’s count down the top 5 comet facts. What are they made of? And what has been their role in Earth’s history?
1. The Oort cloud is a belt of comets around the sun
As previously mentioned, comets are just balls of frozen water and ice. This is the same composition for the comets that exist at the outer edge of our solar system.
The Oort cloud stretches out beyond our most distant planet. It spans a distance of 50,000 to 200,000 AU.
What the Oort cloud is it’s just a belt of mainly comets that travel around the sun.
There’s lots of them. But they’re small and account for a small total volume.
Other than the Oort cloud, comets exist in the Kuiper Belt which is home to many asteroids in the solar system.
2. The anatomy of a comet
The frozen center of a comet is what’s known as the nucleus. This part contains the frozen gas and dust particles.
When a comet passes closer to the sun, comets produce a surrounding glow known as a coma.
These are gases like carbon monoxide, carbon dioxide, ammonia and methane that are released due to solar radiation.
Some comets have tails which are from the effects of solar winds vaporizing. This is part of the nucleus streaming light also due to solar radiation.
3. Comets may have transported Earth’s water
Is the origin of water from volcanoes or comets? By investigating a comet close up, we can truly understand if comets are a better candidate.
Enter the Rosetta mission. This comet-chasing spacecraft was the first to examine a comet in full-on detail.
The mission found that the Rosetta comet to contain a higher ratio of deuterium, which is the heavier form of water found on Earth.
On Earth, for every 10,000 water molecules on Earth, there are 3 deuterium atoms. But comets show significantly higher ratios of “heavy water”
By knowing comets show a higher ratio of deuterium, it makes the theory that water originated from comets less likely.
4. Halley’s Comet regularly swoops past Earth
Halley’s comet is the only comet that regularly orbits by Earth that becomes visibly to the human eye.
The last appearance of Halley’s Comet in the inner solar system was in 1986. The next time it will again be visible is in 2061.
This highly elliptical comet was named after Edmund Halley who used the laws of motion to calculate its orbit.
The nucleus of Halley’s Comet is only about 15 kilometers across. We don’t know its mass but it’s estimated to be about 2.2×1014 kg.
5. Comets struck Earth in geologic history
The evidence of comets impacting the Earth is sparse. It’s a rare occasion, even in Earth’s 4.5-billion-year history.
About 60 million years ago, there is evidence that a comet or asteroid crashed into the Gulf of Mexico. This impact was first revealed from the Chicxulub crater.
Ultimately, this triggered the extinction of the dinosaurs 65 million years ago.
Also, in Siberia, the Tunguska event is the largest recorded impact in history. This impact was either caused by a comet or asteroid.
Overall, there is sparse evidence for comets crashing into Earth and the possibility of getting hit by comets is very rare.